Microscopic Counting of the Total Number of Bacteria and Metabolically Active Bacteria in Soil Samples: Their Relationship and Oscillative Dynamics of Number

Abstract

Experimental results of daily counting under a microscope for 30 days of prokaryotic cells in preparations from soil samples when stained with different specific dyes and literary results on daily counting of bacteria in soil using different methods are presented. The FITC dye, which stains the entire set of bacterial cells, revealed a wave-like dynamics of cell numbers with different numbers of oscillations in the form of peaks in all experiments. Using the SFDA dye, which detects only living, metabolically active cells, wave-like dynamics were also revealed, but their oscillating number was significantly less. The reliability of oscillations and differences in cell numbers when using different dyes were confirmed statistically and by harmonic analysis. The wave-like dynamics of living, metabolically active cells is a consequence of the cycles of growth and death of bacterial cells and short-term trophic succession in the microbial community. External disturbing influences did not affect the manifestation of wave-like population dynamics, both in the population of living cells and in the total number of cells. The phenomenon of wave-like dynamics of non-living bacterial cells and their numerical superiority is explained by the fact that cells, losing viability, lyse and disintegrate not immediately after dying, but with some delay in time. This leads to the accumulation and permanent superiority of the pool of dead cells when microscopically counting the total number of bacteria in the soil and explains the discrepancy in bacterial numbers between different counting methods. The presented experimental and literary material will serve as a substantiation for microbiologists and biotechnologists of the need to control the dynamics of the numbers of introduced populations and communities of microorganisms into the natural environment, as well as a source of knowledge for the successful management of natural microbial communities.